linux-kernel - Re: [PATCH v7 00/27] x86, boot, 64bit: Add support for loading ramdisk and bzImage above 4G

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Date:	Sat, 22 Dec 2012 02:38:29 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 00/27] x86, boot, 64bit: Add support for loading
 ramdisk and bzImage above 4G

On Fri, Dec 21, 2012 at 6:42 PM, Konrad Rzeszutek Wilk
<konrad.wilk@...cle.com> wrote:
> On Mon, Dec 17, 2012 at 11:15:32PM -0800, Yinghai Lu wrote:
>> Now we have limit kdump reseved under 896M, because kexec has the limitation.
>> and also bzImage need to stay under 4g.
>>
>> To make kexec/kdump could use range above 4g, we need to make bzImage and
>> ramdisk could be loaded above 4g.
>> During booting bzImage will be unpacked on same postion and stay high.
>>
>> The patches add fields in setup_header and boot_params to
>> 1. get info about ramdisk position info above 4g from bootloader/kexec
>> 2. get info about cmd_line_ptr info above 4g from bootloader/kexec
>> 3. set xloadflags bit0 in header for bzImage and bootloader/kexec load
>>    could check that to decide if it could to put bzImage high.
>> 4. use sentinel to make sure ext_* fields in boot_params could be used.
>>
>> This patches is tested with kexec tools with local changes and they are sent
>> to kexec list later.
>>
>> could be found at:
>>
>>         git://git.kernel.org/pub/scm/linux/kernel/git/yinghai/linux-yinghai.git for-x86-boot
>
> Did a light test and it looks to work under Xen - thought I had not tested
> any various configuration of memory layouts.
>
> More worryingly it blew up under native under an Dell T105 AMD box with 4GB of memory.
> I can't get it even to print anything on the serial log:

can you try that branch again ? update the #PF handler to clean
init_level4_pgt in all case.

I did not consider when you are xen enabled kernel on bare metal.

aka need to add
          clear_page(init_level4_pgt);

in init_mapping_kernel() of head_64.S

Thanks

Yinghai
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